The invention relates to particulate foam regulating agents which can be used in detergents or cleaners, and to a process for their preparation.
The foam-regulating effect of combinations of paraffins with bis-fatty acid amides in aqueous surfactant-containing systems is known. Thus, for example, European patent specification EP 0 309 931 B1 describes particulate foam regulating agents suitable for use in detergents and cleaners which contain a water-soluble surfactant-free carrier material and, adsorbed thereon, a siloxane-free antifoam mixture of 5-60% by weight of soft paraffin and/or hard paraffin, 20-90% by weight of microcrystalline paraffin wax with a certain melting range and 5-20% by weight of a diamide derived from C2-7-diamines and C12-22-fatty acids in finely divided form. The preparation of such particulate foam regulating agents takes place by means of spray drying an aqueous slurry which comprises the carrier material and the antifoam mixture. The antifoam performance of the antifoam mixture is indicated to be inadequate when it is sprayed onto a particulate detergent.
The use of foam regulating homogeneous mixtures of nonionic surfactant and a foam regulating system which comprises paraffin wax and bis-fatty acid amides for improving the manufacturability and the product properties of extruded detergents and cleaners is known from international patent application WO 96/26258.
German laid-open specification DE 23 38 468 provides a detergent with a content of a silicone antifoam which is protected against interactions with the detergent constituents. To prepare it, aqueous melts which comprise the silicone antifoam and a carrier substance, for example polyglycol, are firstly spray-dried, and the resulting particles are provided with a coating in a fluidized bed of a solid, water-soluble coating material. The coating materials which can be used are customary salts used in detergents, in particular tripolyphosphate or carboxymethylcellulose. Such a multistage preparation process is comparatively technically complex.
German laid-open specification DE 31 28 631 describes the preparation of foam-suppressed detergents with a content of silicone antifoams which are microencapsulated. In this connection, the silicone is dispersed in an aqueous solution of a film-forming polymer and the dispersion—separately from the other detergent constituents dissolved or dispersed in water—is fed via a particular line to the spray-drying plant. The two partial streams are combined in the region of the spray nozzle. Suitable film-forming polymers are, for example, cellulose ether, starch ether or synthetic water-soluble polymers and mixtures thereof. The formation of the microcapsules takes place spontaneously in the spray nozzle or by prior precipitation by adding electrolyte salts to the silicone dispersion. The described process is inevitably connected with the preparation of spray-dried detergents. Transference to detergents and cleaners prepared by other methods, for example by granulation, or even to other fields of use is not possible with this procedure.
European patent application EP 097 867 describes a process for the preparation of microencapsulated antifoam oils by mixing a silicone emulsion with an aqueous solution of carboxymethylcellulose and precipitating the microcapsules by adding electrolytes, in particular polyvalent salts or organic solvents. There are considerable difficulties in homogeneously distributing the small amounts of silicone microcapsules required for adequate foam suppression in a comparatively large amount of washing powder.
German laid-open specification DE 34 36 194 describes a process for the preparation of a pourable antifoam granulate by spray-drying an aqueous antifoam dispersion comprising film-forming polymers. For the purpose of preparing a granulate with a composition of from 1 to 10% by weight of water-insoluble antifoam active ingredient, 0.2 to 2% by weight of a mixture of sodium carboxymethylcellulose and methylcellulose in the weight ratio 80:20 to 40:60, 70 to 90% by weight of inorganic, water-soluble or -dispersible carrier salts, and the remainder water, an aqueous solution comprising 0.5 to 8% by weight of the cellulose ether mixture is swollen at a temperature of from 15 to 60° C. until the viscosity of the solution is at least 75% of the viscosity which is measured for complete swelling of the cellulose ether solution, and then the antifoam active ingredient is dispersed in this solution and, following the addition of the carrier salts and optionally water, the homogenized dispersion is spray-dried. The antifoam active ingredients used are organo-polysiloxanes, paraffins, and mixtures of organo-polysiloxanes and paraffins. The antifoam active ingredient content is 1 to 10% by weight, preferably 3 to 7% by weight. The carrier salt preferably consists of a mixture of sodium silicate, sodium tripolyphosphate and sodium sulfate.
European patent specification EP 0 337 523 B1 discloses a process for the preparation of pulverulent detergents which comprise at least 5% by weight of anionic surfactant, 20-80% by weight of alumosilicate and paraffin wax which is essentially insoluble in water and also anionic and nonionic surfactants, which comprises the simultaneous spraying or subsequent spraying of the paraffin onto the prepared detergent particles as an essential process step. The paraffin wax can here also be used in the form of a mixture with nonionic surfactants.
The variant of spraying the paraffin onto a pre-prepared pulverulent detergent disclosed in the last-mentioned document can only be used with difficulties if it is desired to use the paraffin wax not on its own, but in combination with a bis-fatty acid amide which, as is known, enhances its foam regulating effect. Such bis-fatty acid amides are generally solid at room temperature and have a relatively high melting point, meaning that they, or their combination with the paraffin, can only be handled in liquid and sprayable form at an elevated temperature of, for example, about 140° C. If this temperature is not reached, the pipelines and nozzles used may be blocked by the solidification of the bis-fatty acid amide. It is also disadvantageous that such high temperatures of the spray material may lead to undesired interactions with thermally sensitive constituents of the detergent. In addition, a uniform distribution of the foam regulating system in the detergent is put at risk if, being a spray material heated to high temperatures, it is rapidly cooled after striking the detergent powder.
In international patent application WO 00/36063, it has been proposed to solve this problem through the use of an aqueous foam regulating emulsion which comprises 16% by weight to 70% by weight of foam regulating active ingredient based on paraffin wax and/or silicone oil, 2% by weight to 15% by weight of nonionic and/or anionic emulsifier, and not more than 80% by weight of water. Spraying such emulsions onto solid carrier materials gives very highly effective foam regulators in particle form.
However, the stability of the resulting particles is not always satisfactorily high. Rather, conveyance and transportation of these foam regulating particles may lead to their disintegration into smaller particles or powders which, while still having a good foam-regulating effect, cannot be incorporated directly in a uniform manner into particulate detergents or cleaners.
The problem of inadequate particle stability is solved by the present invention by adapting the carrier material.